1. Field of the Invention
The invention relates generally to the field of photography, and in particular to a film cassette
2. Description of the Prior Art
Commonly assigned U.S. Pat. No. 4,938,429, issued Jul. 3, 1990, discloses a film cassette wherein a pair of annular constraining flanges are coaxially spaced on a film spool. The flanges radially confine the outermost convolution of a film roll wound on the spool, to prevent the film roll from clock-springing against an inner wall of the cassette shell and thus binding against the inner wall when the spool is rotated in an unwinding direction. A pair of internal cam members located on a control shaft accessible at the exterior of the cassette shell are rotatable with the shaft to separate a pair of light-trapping velvet or plush pads in a film egress passageway, by forcing opposite throat portions or lips of the shell apart. Another pair of internal cam members located on the control shaft are rotated with the first pair of cam members to flex respective limited peripheral sections of the flanges apart a distance sufficient to radially free a corresponding longitudinal section of the outermost film convolution, including its leading end. Then, rotation of the spool in the unwinding direction will cause successive peripheral sections of the flanges to be momentarily flexed apart and each freed section of the outermost film convolution, beginning with its leading end, will be advanced through the passageway to outside the cassette shell. A film stripper located on the control shaft is rotated with the cam members from a non-stripping position removed from the film roll to a stripping position for receipt between the leading film end and a next inward convolution of the film roll to guide the leading film end into the passageway as the spool is rotated in the unwinding direction. The stripper is moved to its stripping position when the light-trapping pads are separated and is returned to its non-stripping position when the light-trapping pads assume their original position.